The present invention generally relates to molten metal processes, and, more specifically, to removal of adherent molten metal from surfaces.
Many processes require the use of molten metal. For example, metal bodies or structures can be created by providing molten metal into a die or mold, allowing the molten metal to cool and solidify, and removing the solidified metal structure from the die. Metal/ceramic composite materials can be created by contacting a ceramic body with a molten metal. Molten metal is also used in some heat transfer processes, such as the use of liquid sodium in some nuclear reactor systems.
Aluminum is a metal that is often used in molten metal processes. During the use of molten metals, such as aluminum, some molten metal may adhere in undesirable locations requiring removal of the molten metal. For example, the temperature of a molten metal bath is often measured by placement of protected thermocouples into the bath. The protective cover for thermocouples may be made of iron, fused silica, or other materials designed to minimize reactivity with the molten metal. Upon removal of the protected thermocouple from the molten metal bath, some molten metal will adhere to the protective cover. One method to remove this liquefied metal from the thermocouple protective cover is to wipe the molten metal off with, for example, a refractory cloth of natural or synthetic fiber.
Another example of the need to remove molten metal from a surface is when creating a metal/ceramic composite part or workpiece by non-vapor phase oxidation of the molten metal by submerging a ceramic body into a molten metal bath, or otherwise contacting the body with molten metal, such as disclosed in U.S. Pat. No. 5,214,011. In this process, the molten metal becomes incorporated into the ceramic body and is retained therein. When the body is removed from the molten metal bath, there remains molten metal on the outside surfaces of the body.
This excess molten metal on the body is removed by scraping, wiping, or swabbing the molten metal, such as with refractory cloth, but these methods are time consuming and difficult to use effectively for small pieces or intricate surfaces. Further, with respect to the process described in U.S. Pat. No. 5,214,011, these techniques are inadequate, because molten metal may continue to exude from the workpiece to the body surface following the initial cleaning, thus requiring additional and continual swabbing as the part cools.
If the molten metal is allowed to remain on the body, protected thermocouple, etc., the molten metal may react with the surface to form undesirable products, damage the surface, or harden/solidify on the surface creating functional or aesthetic problems.
Surface finishing of metal structures may be conducted by processes such as grit blasting, but such processes generally are not suitable for removal of metal that has not hardened or solidified. Moreover, grit blasting will likely damage or remove some of the surface, as well as any molten metal such a process may remove.